'We know the toddler absolutely needs to engage all his senses,' he said.

Dr Tisseron is by no means anti-technology - the 64-year-old is himself an avid video gamer - but until more research has been carried out, he recommends keeping screens out of baby hands.

In the first two years of life, the brain triples in size, synapses forming as young children experiment with objects they sniff, bite and throw.

Despite the iPhone and iPad's much-lauded interactivity, Dr Tisseron says they remain limited in terms of sensory experience: They can engage sight, hearing and touch - to an extent - but not taste or smell.

And some parents worry about computer culture interfering with the way their children play with conventional toys.

'But he gets very frustrated when the pictures don't move, and I think that is really coming from the pervasive culture of video and animation.'

The simplest of toys, and baby games with no set rules, are crucial, says Texas paediatrician Ari Brown, lead author of an American Academy of Pediatrics report last year on screen use by children below the age of two.

'There are some pretty good apps and activities that encourage problem solving, memory, ordering, sequencing - virtual versions of games we used to play as kids,' Dr Brown said.

But 'no app can replace the value in taking two blocks and figuring out how to stack them one on top of the other'.

Dr Brown suggests the main danger is a kind of opportunity cost: When youngsters play with iPads, they are not engaged in what may be more beneficial.

That view is shared by Mr Jean-Philippe Vieira, a 46-year-old cook, who has neither a tablet nor mobile phone and limits his children's television time to 20 minutes on Friday.

He believes toddlers need space to invent their own games, the way he did growing up in Portugal.

'There were moments when we had nothing to do, but that was great because when you do nothing, you come up with ways to occupy yourself. You don't need technology to play,' he said.

Still, George's parents are not concerned. Both graphic artists, they recently developed their first app, which generates firework-like images to save as screenshots.

Now they have seen first-hand what toddlers like - catchy colours, sound, large buttons and simplicity - the pair plan to develop child-friendly apps.